Re: GDBserver ports cleanup

[Simon Marchi <simon.marchi@polymtl.ca>]

On 2020-05-13 8:01 a.m., Pedro Alves wrote:
> On 5/12/20 9:26 PM, Christian Biesinger via Gdb-patches wrote:
>> On Tue, May 12, 2020 at 11:48 AM Simon Marchi via Gdb-patches
> 
>>> About Windows support for ARM, I don't really know about it.  I think that our port
>>> was targeting Windows CE [2], which can probably be considered obsolete.  However,
>>> Windows 10 supposedly runs on ARM [3], so it might be relevant to keep it?  I don't really
>>> know if the current GDBserver code would help for that or not.  In doubt, I won't propose
>>> to remove it.
>>
>> If indeed the win32-arm support handles Windows 10, I think it would
>> be good to keep it, but I am not sure it does -- win32-arm-low.cc does
>> have these lines:
>> /* Correct in either endianness.  We do not support Thumb yet.  */
>> static const unsigned long arm_wince_breakpoint = 0xe6000010;
>> #define arm_wince_breakpoint_len 4
>>
>> Note mention of WinCE. Also, I am not so familiar with Thumb but I
>> believe that's widely used on ARM these days?
>>
>> So my vote would be to remove this for now and if someone wants to
>> revive it there's the git history.
> win32-arm support in gdbserver is only for Windows CE.  I was the one
> who wrote it, it was the reason I got into GDB hacking in the first
> place.  :-)  There was no Windows for ARM back then.  
> 
> I don't object removing it.  I haven't built a compiler or gdbserver
> for WinCE in years, and I doubt anyone else has^W^W^W^W^W^W^W^W^W^W^W^W
> Wow, I just found out that someone forked my old cegcc project, and
> updated it based on a much more modern GCC:
> https://max.kellermann.name/projects/cegcc/
> I had no idea.  Look like he has some local GDB in his github, though
> dated from 2016/2018.
> 
> If you do remove it, then you'll want to remove all the code guarded under
> _WIN32_WCE in win32-low.cc, and also wincecompat.c.  There's also
> ARM WinCE support on the GDB side, in arm-wince-tdep.c.
> 
> I'm not sure there's that much salvageable for an eventual Windows for ARM
> port.  For example, Windows for ARM is strictly Thumb-2, while I don't recall
> ever considering Thumb-2 back then.  WinCE was FPA, I believe, while Windows
> for ARM is VFP.  The ABIs are just different, and WinCE is weird beyond belief.
> (no "errno", no concept for "current directory", etc.).
> 
> Other than nostalgia for being what got me into GDB, I really won't miss it
> myself.

Thanks for the storytelling, I enjoyed it :).

If removing support for WinCE ends up simplifying win32-low.cc, it is a net gain,
since that file is used today.

Simon